Since you're on a laptop, you're pretty much stuck with what you've got. FSX will run ok on your system. Yes, there are plenty of issues running FSX - that's just one of those "you learn as you go along" type of things I'm afraid. There are a couple of tutorials floating about that speak to tweaking - and FSX is probably the worst "game" I know of that "needs" to be tweaked in order to run well. That being said, why not just get it, get VLC, dive in, try the settings at around medium, and see how it goes.
If you search through NZFF, you'll find plenty of discussion about tweaking & settings and stuff - including all our personal preferences re: Intel vs AMD, nVidia vs ATI and such. Specifically, the 'Technical Issues' section is the place you want to go.
You will find there is a lot of opinion that goes into tweaking and using FSX. You'll see that some people will swear that this thing works, another say that, and everything in between! That's because we're all running different rigs, with different screen resolutions (and the higher the res the better the pic but the more strain on the computer), and different abilities at tweaking / optimising. You'll also find that people have different expectations. For me, unless it's almost real-world, it's not good enough. For others, instrument flying from A to B - outside imagery be damned - is the name of the game.
So, you've got your work cut out sifting and finding your comfortable, operational "niche" for your rig and your expectations. Just don't forget to enjoy the sim somewhere along the way!

EDIT: PS - Don't forget to get SP2 loaded into Vista before you start, and get a good defragger like MyDefrag from
www.filehippo.com to sort your hard drive before you install FSX.